Preparation of siliceous catalyst beads containing free magnesia



March 17, 1953 T. H. MILLIKEN, .1R 2,631,983

' PREPARTION OF SILICEOUS CATALYST BEADS CONTAINING FREE MAGNESIA FiledDSC. 29, 1948 Patented Mar. 17, 1953 UNITED STATS NT OFFICE vPREPARATIONOF SILICEOUS CATALYST BEADS CONTAINING FREE MAGNESIA Applicatin December29, 1948,'sera1N0. 67,987

The present invention relates to catalytic hydrocarbon conversionprocesses employing siliceous plural oxide catalysts and is particularlyconcerned with the preparation of such catalysts and their use incracking of hydrocarbons in the production of desired liquid fuels oflower boiling point, such as gasoline.

The catalysts most widely used for hydrocarbon conversion processes ofthe type described include natural materials such as acid-activatedsub-bentonite clays, and synthetic gels such as silica-alumina. Thesubstitution of other metal oxides in whole or in part for the aluminain synthetic siliceous gel catalysts is also known. Among these,interesting results have been obtained with catalysts such assilica-inagnesia and silica-alumina-magnesia, because of theirselectivity in producing from a heavier charge stock good yields ofliquid hydrocarbons in the gasoline boiling range.

In the preparation of siliceous plural oxide gel catalysts one of themethods in practice is to dry a hydrogel or gelatinous precipitate andto grind the obtained gel to desired size for use in i'inely powderedcondition as catalyst in so called fluidiaed systems of hydrocarbonconversion. In other systems of hydrocarbon conversion, larger masses orpieces of catalyst are generally preferred, which may be prepared byforming ground dried gel into aggregates, for instance such ascylindrical pellets.

In contrast to the above described methods of catalyst preparationinvolving subdivision of a previously formed gel, catalyst has also beenprepared by methods in which the original conformation of the gel as setis maintained during subsequent drying and nishing operations. Thelatter type method is employed particularly in the preparation ofsubstantially spherical or spheroidal bodies of gel, known as beadswhich are produced, in controlled desired average size range, by settingdroplets of hydrosol in a fluid medium, generally in a liquid immisciblewith the hydrosol. The bead catalyst so produced, although havingcertain advantages particularly froin the standpoint of facility ofpreparation, is less porous than finely ground gel catalyst oraggregated bodies formed of ground gel, which difference in porosity isparticularly evidenced by the slower regeneration rates ordinarilyobtained in use of the bead catalyst.

In my copending application, Serial No. 529,594, led April 5, 1944 (nowissued as Patent No. 2,487,065), of which the present application is acontinuation-impart, certain procedures are described for enhancing theregenera- 5 Claims. (Cl. 252-448) tion characteristics of catalystproduced by methods in which the original conformation of the gel as setis maintained during subsequent drying and finishing operations,including bead catalyst. In accordance with the methods thereindescribed, the catalyst acquires a more open structure and is morereadily and more rapidly penetrated by fluids. This opening of the gelstructure is obtained by incorporating in the initial hydrosol, fromwhich the gel is formed, certain finely divided powdered materials whichare distributed through the hydrogel during setting. When such powdersare of proper size range and are present in certain volumetricquantities as specified in said prior application, additional advantagesensue; for instance, drying of the hydrogel pieces is facilitated andbreakage of the pieces otherwise occurring during drying is materiallyreduced. As indicated in said prior application, the powders thusincorporated in the gel may be relatively inert materials or maycomprise finely divided gels or metal oxides which contribute to theproperties of the catalyst, as catalytically active materials,promoters, or the like.

The present application involves an extension of the principle andadvantages described in the said parent application, resulting in newand additional advantages in the methods of catalyst preparation and inthe use of such catalyst in hydrocarbon conversion operations,particularly in cracking of petroleum oils for the production ofgasoline.

In accordance with the invention of the present application the powder,incorporated in the sol and retained in the hydrogel setting therefromis magnesium oxide (which may be in the form of hydrous oxide, hydrate,or hydroxide), a material which is catalytically active in associationwith the inorganic oxide component or components of the hydrogel. Thesol is one capable of setting to a siliceous hydrogel, which may beessentially hydrated silica, alone, or in association with a catalyticnon-reducible metal oxide, such as alumina. The preferred catalystsprepared and used in accordance with the invention comprisesilica-magnesia and silicaalumina-magnesia as beads of open structureand improved regeneration characteristics, prepared by incorporation ofactive powdered magnesia into a siliceous hydrosol, and maintaining themagnesia therein in particulated form as such or as an insolubilizedderivative thereof, at least during the setting of the hydrogel beadsand the drying of the same.

Various methods may be employed for the formation of the hydrogel beadscontaining incorporated powder. Several preferred techniques areillustrated in the accompanying drawings, wherein Figure 1 is anisometric view, largely schematic, of one form of structure that may beemployed in bead formation; Figure 2 is a vertical cross-section on anenlarged scale through a portion of the device shown in Figure 1,comprising generally the mixing head and discharge nozzle; Figure 3 is aschematic representation of an alternative embodiment, usefulparticularly for the production of smaller beads; Figure 4 is a planView, partly broken away and shown in section taken along line @-6 ofFigure 3; Figure 5 is a schematic representation of a furtheralternative modication of a mixing and emulsifying device; Figure 6 is aflow diagram illustrating the preferred sequence of steps in forming andprocessing of gel beads. The operation of these and. other alternativeembodiments will be fully understood from the description below.

The magnesium oxide is incorporated in the siliceous sol rin the form offine particles, which are suspended in the sol and remain substantiallyuniformly distributed therein during the setting of the sol to hydrogel.For this reason it is advantageous to employ rapidly setting sols, forinstance sols which set in about 5 seconds or less, so that themagnesium oxide powder becomes xed in the sol and has little opportunityand preferably less than 35 microns, to provide the desired opening ofthe gel structure such that the rate of regeneration of the catalyst issigncantly increased. To fully obtain the additional advantages offacilitating drying and reducing breakage during drying, the powdershould be present in controlled quantities, as will hereinafter appear.

In the production of spheroidal gel bodies containing incorporatedpowder, such as magnesia in the present instance, the powder may besuspended by being directly mixed with the sol, or preferably the powderis admixed with one of the reacting solutions from which the sol is tobe formed. To this end, the methods and apparatus described in U. S.Patent Nos. 2,384,455 and 2,385,217 may be employed in suspendingdroplets of the sol containing the incorporated powder into a quiescentbody of water-immiscible liquid. With rapid setting hydrosols, however,it is preferred to employ a type of apparatus and procedure such as thatdescribed in my cepending application Serial No. 41,983 iiled August 2,1948 (issued March 11, 1952, as U. S. Patent No. 2,588,402), one form ofwhich is illustrated in the accompanying drawings Figures 1 and 2.

If desired, as may be the case with very small spherical or spheroidalbeads, particularly below the order of about 200 a diameter (in dried orcalcined state) the sol may be emulsied in the water immiscible mediumby rapid agitation to Vform thereby droplets of required size range,

including all of the reactant solutions of the sol. The term hydrogel,as used herein, is distinguished from the gelatinous precipitate which,when formed, is suspended in the liquor of the sol.

The required ne subdivision of the powder to be incorporated may beobtained by precipitating magnesium oxide and grinding the precipitateto desired size, with or without previous drying. The particle size ofthe obtained precipitate may also be controlled by selecting theconditions of precipitation, thereby avoiding the necessity forextensive grinding. Thus, a soluble magnesium salt, such as magnesiumchloride, may be precipitated by conversion to carbonate. The carbonateis formed as a ne pulverulent precipitate which is converted to theoxide by heating, retaining its pulverulent form.

Magnesia of suitable properties for use in accordance with the inventionis readily available commercially. It is supplied in a very bulky formknown as Light Magnesia and in a dense form called Heavy Magnesia.Either form may be used for incorporation in the sol. Magnesia is alsoreadily prepared in precipitated form by addition of alkali or ammoniato an aqueous solution of a magnesium salt such as magnesium sulfate atsuitable pH.

Magnesia, under suitable conditions takes up water, reforming magnesiumhydroxide. It is believed, that when magnesia is incorporated in the solsuch hydration initially occurs with subsequent reaction of theresulting hydrate or hydroxide with the components of the sol or of thewet hydrogel during setting, so that at least a part of the magnesiumbecomes incorporated in chemical combination as a complex with thesilica, or with silica and alumina. For this reason it is best to employa magnesia which has not been calcined at such high temperatures as torender the same practically non-hydratable under the conditions..Accordingly, where the magnesia is to form an active component of thegel the use of dead burned magnesia, or magnesia which has been calcinedat a temperature above 2,500 F., is not advised.

Rapid setting of the hydrosol to the gel state is favored by hightproduct concentration of the components forming the solid phase of thehydrogel, with the added advantage that compositions of high productconcentration tend to produce firmer hydrogel beads, better capable ofwithstanding subsequent handling and treating in the finishingoperations, and resulting in hardier dried beads with lesser quantitiesof broken fragments. Since, moreover, the hydrogel formed from reactantsin high product concentrations will have comparatively lower watercontent, considerable savings in drying costs are gained, and milderdrying conditions may be beneficially employed to elfect drying in areasonable time. Rapidity of setting is also dependent upon the pH ofthe hydrosol as well as on temperature, either of which factors can bereadily controlled to provide additional adjustment of desired settingtime. For practical operation in the preparation of silica hydrogel orsilica-alumina hydrogel containing incorporated magnesium oxide, it ispreferred to employ concentrations, compositions, and conditions suchthat the hydrosol is set to hydrogel in no more than about .5 seconds.Employing the preferred apparatus and the manipulative procedureshereinafter described, hydrosols setting as rapidly as 1% second can behandled.

An optimum pI-I range obtains forv hydrosols of particular compositionat which most rapid setting will occur. With silica as well assilicaalumina hydrosols most rapid setting takes place at between about5 to 9 pH, the setting time increasing with both higher or lower pHoutside of this range. Within the indicated pH range, silica-aluminahydrosols setting in less than 0.5 second are readily obtained withproduct concentrations above about 80 grams S102 and A1203 per liter ofmixed reacting solutions (not considering MgO powder). Compositionsgoing up to 125 grams per liter and somewhat higher (not considering theadded powder) product concentration carn be readily handled by methodsherein described. WithinV the designated optimum pH range for rapidsetting, silica hydrosol will set to hydrogel in about one-half secondor less at a product concentration above about 100 grams per liter SiDz,and compositions of even higher product concentration than in the caseof SiOz-AlzOs can be handled without unusual difficulty.

Coming now to the preferred method for forming siliceous beadscontaining incorporated magf nesia. An apparatus that may be employed inpractice is shown in Figures 1 and 2 of the accompanying drawing.

The illustrated apparatus comprises an outside liquid container I,provided with a vertical wall 2 forming its cylindrical section, and adownwardly converging wall 3 forming a funnelled lower section whichcommunicates with a discharging sluice pipe 4.

Within the external tank I there is suitably supported an internalcylindrical tank 5 closed at the bottom, and forming an annular chamber.8 between the wall 2 and the outer wall of cylinder 5, in the upperportion of the tank In operation, the funnelled lower portion of tanlr lis iilled with liquid, such as water or other aqueous solution, up toapproximately the level of the closed bottom of the inside cylindricaltank 5, or to some extent above or below that level, and a waterimmiscible liquid such as an oil is supplied thereabove, as indicated bythe liquid interface at 1 between the two liquids. The exact level ofthe water in the tank is not important, provided there is suiilcient oilin the annular chamber above the Water level for the purposeshereinafter explained. A continuous supply of water or other aqueoussolution into the lower part of the tank is furnished by means of asupply line S. By modifying the rate of liquid supply through line 8With respect to the discharge rate through sluice pipe 4, the level ofthe interface 7 can be raised 4or low-ered.

Water immiscible liquid, such as oil, is supplied in the annular chamber6 by means of a valve-controlled supply line 9. The upper level of theWater immiscible liquid in the 'tank is maintained by means of slots IIJor other openings formed in the outside wall 2 near the top of the tank,said slots or other openings permitting the water-immiscible liquid tooverflow into a `pan suitably mounted on the periphery of wall 2 andextending over a desired circumferential portion of such periphery. Oneor more of such pans communicating with openings in the wall may beprovided; two being here shown. Each of the pans communicates with acollecting pipe I2, which pipe may be connected to a storage reservoiror to a suitable pumping system operatively connected to line 3 forrecirculation of overowed cil `continuously or intermittently asdesired.

A supporting structure generally indicated by ,I3 is mounted above theupper level of the tank` I, on which structure are mounted the operatingand power-transmission mechanism, including a prime mover such as anelectric motor designated at lf3, and gearing I5 and I6 operating torotate the drive assembly. A bearing housing |'I is affixed to thesupporting structure I3 and thereby suspends the driven shaft andcomponent parts above the center of tank I.

The driven structure includes a rotating shaft I8, to which are attachedliquid conducting lines I3 and 2U, which lines are positively moved in acircular path by the rotation of shaft IS. These liquid conducting linesI9 and 20 communicate with and are attached toeJ streamlined boatshapedmember 2| comprising the mixing head, which member is thus moved in acircular path concentric with the annular space E; the motion of theshaft I3 being transmitted through lines I9 and 20.

The shaft I8 is formed with a central upper vertical bore and anon-communicating central lower bore, through which bores reactantliquids are introduced. These bores respectively communicate with theconducting lines I9 and 20 for conveying liquids to the mixing chamberformed in the mixing head 2|. The reactant liquids enter the mixing head(as particularly shown in Figure 2) and are admixed therein at a highvelocity as a result of jet action. The streamlined body forming thehead 2| is made of a corrosion-resistant material, such as Lucite orother plastic, and is provided with vertical bores 22 and 23 at theupper surface thereof, which bores pass only partly through the body, asshown. The bores 22 and 23 at the upper portions thereof arecounterbored and screw threaded to receive respectively the downwardlydirected elbows of liquid conducting lines IS and 20. The head 2| isalso provided with a central horizontal bore at the lower portionthereof extending from the front to short of the center as indicated at24, and with a horizontal bore extending from the rear to short of thecenter as indicated at 25; the two passages thus formed being connectedby a communicating `bore of reduced diameter in alignment therewith asindicatedr at 26. The vertical bore 22 thereby communicates with thehorizontal bore 2li and the vertical bore .23 communicates with thehorizontal bore 25. The portion of the bore 25 eX- tendingfrom the innerterminus of bore 24 to the side Wall of bore 23 is screw threaded toreceive a correspondingly threaded jet member 27 provid-ed with anenlarged portion forming a boss 2B adapted to t closely within the bore24. This enlarged portion of the jet member is provided at its uppersurface with a recess 29 corresponding to and communicating with bore22; the recess may be readily formed in proper position by boringthrough the boss 28 While the jet member 2l' is in place in the head 2I.

Beyond the screw threaded portion of the jet 2T and opposite from theenlarged portion 28, the diameter of the jet member is further reducedas indicated at 30, the jet member ultimately ending in a taperedportion 3| extending, when the nozzle is inserted Within the head 2|,beyond the intersection of vertical bore 23 with horizontal bore 26. Thejet member 2l is centrally bored horizontally to provide a passage 32,which is oi reduced diameter at the rear thereof. The front of thepassageSZ is closed by a plug member 33, access to the passage may behad through the front opening in the head 2| provided by the bore 24,which opening in normal operation may be closed by a removable closuremember 31%, the outside of which conforms in general to the contour ofthe front portion of the head 2|.

Within the bore 25 in head 2| there is inserted a tightly fittingtubular nozzle member 35, centrally bored as indicated at 36 through themajor part of its length, and provided at the front end thereof with atapered bore paralleling the tapered portion 3| of the nozzle member 2l.The tubular member 35 is held in place by a set screw 37 insertedthrough the bore 38 at the upper portion of the head 2|. The tubularnozzle member 35 contains a tube 39 formed of a yieldable plastic, suchas tygon, extending beyond Y the rear extremity of the nozzle member 35,and

held in place therein by a compressing and retaining cap l0 screwthreaded onto the member 35. The inner wall of the cap is slightlytapered at 4| to compress the end of the tube 39 and thereby reduce thesize of the discharge opening of the tube. This taper may beapproximately such as to reduce the diameter of the outlet orifice byabout 1A; the internal diameter of the tube 39.

The internal taper at the forward end of the tubular member 35 is suchthat the same operates as a reducing adapter between the diameter of thebore 26 and the inside diameter of the tube 39, thereby providing anabuttment within the member 35, against which the tube 39 is pressed bythe cap 40.

To assure uniform rotation of the shaft i8 and to reduce vibration inthe system, the shaft may be provided with a counterweight W supportedon an arm projecting radially from the shaft dametrically opposite thelines I3 and 2li.

For convenience of illustrating the operation employing the type ofapparatus thus far described, it will be assumed that a silica-aluminahydrogel containing magnesium oxide is to be prepared. In this case, thereacting solutions may comprise an alkali metal silicate, and analuminum salt solution or alkali metal aluminate solution containingacid or alkaline agents, to give the desired pH. The powder may beincluded in either f the reacting solutions, but is preferably addedwith the silicate solution. The silicate solution, which may be acommercial water glass (for instance N-Brand) is admitted from anysuitable proportionating or flow regulating means through a supply line42, the solution passing through communicating channels into the bore 22in the head 2|, nally entering into the tube 3S by passing through thebored channel 32 in the jet 2. The alumina component may be furnished byan aqueous solution containing aluminum sulfate and sulfuric acid inrequired amount to obtain the desired pH. This solution is admitted inregulated quantity from a suitable supply source through the tube 43 andpasses by communicating channels to the head 2|, entering the annularspace provided between the wall of the bore 2S and the jet member 2'!and passing through the annular space between the parallel tapered wall3| and the correspondingly tapered wall of the nozzle 35 into the tube39, wherein it becomes admiXed with the silicate solution and isthoroughly agitated therewith as a result of jet action and the modifiedventuri effect. The reaction mixture containing the incorporatedmagnesium oxide then flows along tube 33 in which hydrosol formationtakes place and the formed hydrosol is forcibly ejected therefrom as aresult of the pressure of the feeding of withdrawn,

the solutions through the tapered portion 4|, the hydrosol beingprojected as a stream which falls upon the surface of the oil in thetank I. The reaction producing the hydrosol will generally be completedbefore the reaction mixture is discharged from the tube 39, but thepossibility of continuing reaction beyond is not excluded.

In the preparation of silica gel, the reacting solutions introduced maybe an alkali metal silicate and a mineral acid, such as hydrochloric orsulfuric, in concentration and amount furnishing the desired pI-I.

In the preparation of comparatively large beads (for instance of l mm.diameter or above in shrunken, dried or calcined state), it is advisablethat the head 2| and the nozzle member 35 be maintained slightly abovethe surface of the oil in the tank, to avoid substantial agitation ofthe oil by the movement of the head. It is preferred, in any event, thatat least the final set of the hyrogel take place at a level in the oilbath which is not being materially agitated.

The speed of rotation of shaft I8, and thereby the linear velocity ofmovement of the head 2|, is controlled by suitable means (not shown),and is correlated with the ow rate of the reactant solutions into thenozzle 35, so that the rate of movement of the discharge outlet of thenozzle is approximately equal to the rate at which the hydrosol isdischarged therefrom, but opposite in direction thereto. Under theseconditions the discharge stream has no horizontal velocity component, orat least an immaterial one.

In the operation of the embodiment thus far described, it is preferredto employ an oil of lower specinc gravity than that of the hydrosolentering the oil bath. The stream of hydrosol will then settle throughthe body of oil, and as a result of the interfacial tension between theoil and the hydrosol, the latter is broken up into globules whichcontinue to settle in the body of the oil. lThe body of oil ispreferably of sufficient depth to allow setting of the hydrogel to takeplace therein, so that the set hydrogel globules continuing theirsettling in the oil pass through the interface between the oil and thewater or aqueous solution. The water or aqueous solution also operatesas a carrier fluid to convey the wet hydrogel beads to storage or tofurther treatment.

As illustrated in the flow diagram (Fig. 6), the wet beads are broughtby the aqueous liquid to a suitable tank, from which they maybe in batchor continuous operations, for further processing. Thus, as shown, thehydrogel beads in the aqueous liquid may be conveyed to suitableequipment for hot aging of the hydrogel (if that step is to bepracticed). In the hot aging" treatment a portion of the carrier liquidmay be heated and recirculated in contact with the wet hydrogel beadsfor a desired time. Aqueous liquid not required in supporting thehydrogel beads during transportation will be returned to the supplysource for constantly replenishing the aqueous liquid in the settingtank I.

The size of the formed hydrogel globules and accordingly of the ultimateshrunk beads (after drying) will be determined to a certain extent bythe diameter of the stream issuing from the discharge nozzle 35 and thevelocity of the stream relative to the body of immiscible liquid. Otherfactors entering into the determination of the degree of sphericity aswell as the size of the coagulated particles may VYthe top forseparation.

sication may be obtained paratively small the mixed reactants or theresulting hydrogel beads formed in the process include: the viscosityand density of the body of immiscible liquid as well as the viscosityand density of the hydrosol; and the interfacial tension between theparticular immiscible liquid and the hydrosol in any given system.

In connection with the described embodiment, the liquid in which thesetting of hydrosol to hydrogel takes place may be any liquid orcombination of liquids substantially immiscible with water, andpreferably liquids having a lower speciiic gravity than the hydrosol;such as: petroleum naphthas, kerosene, hydrocarbon oils; halogenatedhydrocarbons such as carbon tetrachloride or perchlorethylene;alkylesters or car- Yboxy acids Ysuch as .dialkyl phthalates, for` eX-ample dibutyl phthalate; etc., or physically compatible mixtures of theliquids recited giving desired density and viscosity. It is preferred toemploy immiscible liquids of high viscosity compared with the hydrocol,since these tend to give beads of more uniform shape and size.

In using the emulsication technique for the production of beads, thehydrosol containing the incorporated powder substantially uniformlydistributed therein, is emulsied in the Water immiscible liquid and thedroplets of sol therebt7 formed are maintained in emulsified form untilthe sol sets as hydrogel. This operation may be practiced as a batchprocedure wherein the hydrosol and the immiscible liquid which willconstitute the external phase of the emulsion are brought together andviolently mixed or agitated as by means of a turbine stirrer. In generalany of the types of water-immiscible liquids above mentioned inconnection with the previous embodiment, may likewise be utilized foremulsication. In the batch operation there should be employed at leastone volume of water immiscible liquid per volume of sol to be emulsiedtherein. When the immiscible liquid is of lower specific gravity thanthe sol, the emulsified material may be allowed tosettle to the bottomof the oil phase after the droplets have set to hydrogel; while if aliquid heavier than the liquid hydrosol is employed as the externalphase, such as carbon tetrachloride, the be allowed to arise to Insteadof operating by batch meth-ods, the

` hydrosol and the immiscible liquid may be emulsiiied by continuouslyfeeding streams of the two liquids into admixture in regulated amounts.

The requireddegree of agitation to effect emulbv the use of Separatelycontrolled stirrers and/or by the velocity of either or both of thestreams.

A suitable system for producing beads of comparticle size is illustrated1n Figs. 3 and 4. In the operation of this illustrated embodiment, oneof the reacting solutions containing powder may be introduced into theside inlet of a jet mixer (see Figure 4), and the other reactantsolution injected thereinto through a nozzle |01. Thus the two solutionsare violently admixed in the zone |02. and hydrosol formed, as the casemay be, is ejected through the discharge nozzle |03 into 'the oil bath|04. As a result of the impact of the liquid being injected into the oilbath at high velocity, and violent local agitation incident thereto, atleast a temporary emulsion of drop-lets of hydrosol in the oil bath isobtained. Employing an oil which is lighter in gravity than the formedhydrogel globules, the latter will pass out of the zone of agitation andthrough the oil-water interface at |05 into a body of water or diluteaqueous solution below which also operates as a transporting liquid. Thehydrogel beads may be conveyed in and by the aqueous medium, as by meansof a conduit |05, to a drain generally indicated at |01; the drainedliquid being returned by a conduit as indicated at |08 to the body ofaqueous medium for reuse.

A quite simplied but highly efcient device that may be advantageouslyemployed in forming small beads by a continuous emulsification procedureis illustrated in Figure 5. In the operation of this embodiment, one ofthe reactant solutions, say the sodium silicate containing powderedmagnesia, is introduced at high velocity through line ||0 into a chamberIII. There is also introduced into chamber through a side line ||2, theother reactant solutionsuch as an acid or an aluminum salt solutionwhich may contain acidic or alkaline substances. The two solutions areviolently adniixed in the zone H3 in chamber and forcibly ejectedtherefrom through discharge nozzle ||4 into a surrounding mixing headH5. Oil or other water-immiscible liquid is introduced into the mixinghead H5 through a side line IIB, and there contacted with the previouslyadmixed reactants or the hydrosol resulting therefrom, in the mixingzone This results in violent agitation and intimate admixture of oil andhydrosol because 0f the impact and velocity of iow, so that a inedispersion of droplets of hydrosol in oil is obtained. The dischargenozzle ||8 from the mixing zone ||1 t0 the tip i9 is preferably ofsuitable length consistent with the setting time of the hydrosol thatsetting takes place therein. lThus, minute beads of hydrogel distributedin oil are discharged at the tip H9. The hydrogel beads may bedischarged with the oil into a tank containing water or aqueous solutionfor separation from the oil, the separated oil being returned for reusethrough pipes connected to line IIG. If desired, lcentrifugal or othermeans for separating oil from the beads may be employed, particularlywhen formed at high product concentration and therefore having suicientstrength in Wet State to withstand such operations.

The device just described is particularly efficient for use with veryrapidly setting hydrosols and offers further advantages in enablingemulsication with comparatively small quantities of oil, therebymaterially reducing required size and cost of equipment.

The size of the nished gel particles after drying will depend upon. theinitial size of the Wet hydrogel beads, which in turn is controlled bythe size of the emulsiiied droplets. In general the emulsicationtechnique, whether employing the illustrated embodiments, the describedbatch method, or other continuous methods; is best adapted forproduction of beads which when shrunk. in drying are of an average sizebelow about 200 microns and largely in the range of about 50-200microns. By increasing the effectiveness of the emulsication forinstance by increased rapidity of agitation, particles of less than 50micron size predominantly, may be produced if desired.

The aqueous solution employed as a sluicing or carrier liquid inconnection with the embodiment illustrated in Figure 1 or thatillustrated in Figure 3, is preferably a dilute salt solution of properascisse l1 specific gravity to support the oil above. For this purposedilute aqueous solutions of salts which are relatively inert withrespect to the hydrogel may be employed. For instance a 5% to solutionof sodium sulfate (NazSOi) Vhas been found satisfactory for the purpose.

In any of the methods of bead formation above described, the magnesiumoxide powder may be incorporated by suspending the same in either of thesolutions introduced into the mixing zone in which the final reactantsolution or the hydrosol is formed, or the powder may be added through aseparate inlet to the mixing zone as a slurry or suspension in acompatible liquid, such as water.

It should be noted in passing that by the inclusicn of the powder, thesetting time of the hydrosol is accelerated; so that reduced productconcentration of the principal reactants is required to effect settingin any given time. For instance, a composition of about 8 to 9 pH havinga product concentration of 100 grams Si02 and A1203 per liter will setin about 1A; to 1/2 second at about room temperature. With theincorporation of a suicient quantity of powder in the composition,setting will take place under like conditions and in about the same timeat product concentration of the S102 and A1203 in duced breakage, and toprovide a bead of desired open structure which can be rapidlyregenerated, the magnesium oxide should be employed in a size of lessthan about microns and preferably of about 5 to l5 microns average size.It is pointed out in my parent application Serial No. 529,594hereinbeiore identified, that the quantity of powder to be employed isbest measured on the basis of volumetric ratio to gel, because ordifferences in density of the various powders that may be employed. Thepreferred volumetric ratio therein indicated lies in the range of 0.35to 1, determined as the ratio of the weight percent of powder dividedlby the apparent density of the powder, to the weight percent of geldivided by the particle density (chunk density)V of the gel. Measurementof the apparent density of the powder is made by placing a weightedsample of the powder in a metal cylinder of known volume per unitlength, inserting a closely tting piston on top of the powder andtamping the piston until no further contraction of the body of powder isobserved, the tamping being done with a light hammer. Accuratemeasurement can lbe made when the total length of the cylinder occupiedby powder' is approximately one inch in a cylinder approximately oneinch in diameter. When a longer cylinder is employed, say one of eightinch length, it has been observed that proper packing is obtained at theends of the cylinder but not intermediate its length. The chunk densityof the gel is obtained by drying samples of the gel without any includedpowder. Such chunks of gel, unless dried with extreme caution, willpractically all break down to smaller pieces. This, however, does notvitiate the measurement of the chunk density. Prior to measurement thedried gel is heat treated, as for example, at 14:00o F. for l0 hours, toproduce normal shrinkage. A sample of the largest pieces obtained afterheat treatment is weighed and the voids in the pieces of the weighedsample are saturated with water.

Elevation of temperature also accelerates All surface water, in so faras possible, is removed. The chunk volume is then measured in apycnometer.

Within the above indicated volumetric range of powder to gel light orheavy magnesia can be used, so long as at least about 10% to 15% ofmagnesia by weight of gel is thereby provided. The presence of thisminimum weight quantity of magnesia is prescribed, because ashereinafter explained, a portion of the magnesia introduced is intendedto become chemically associated with components of the gel, and in sodoing may be dissolved and be no longer present in particulate form. Theportion which may be thus dissolved will depend upon the manner in whichthe hydrogel is processed and iinished, which can be controlled to varythe amount of magnesia which will become associated as an activecomponent of the catalyst, thereby offering a certain degree ofiiexibility by which the properties of the final dried catalyst can bevaried as desired. By proper control of the processing of the gel up toabout and as little as desired Of the incorporated powder can beretained in the hydrogel as powder, while obtaining active catalystshaving in general the characteristic catalytic properties ofsilica-magnesia or silica-aluminamagnesia.

Although the quantity of introduced magnesia powder as well as thequantity which is retained as powder during nnishing and drying of thehydrogel may be varied over a fairly wide range as above indicated, itmay be stated as a general rule that bead catalysts of improvedproperties are obtained when there is introduced into the hydrosol anamount of magnesium oxide powder equal to about 20 to 50% by weight ofthe gel to be produced (on C. dry basis) whether the hydrosol be ofsilica alone or of silica-alumina. With this quantity of magnesiapowder, under most conditions, sufcient magnesia is provided (l) forchemical combination with components of the gel to produce catalysts ofdesired activity and selectivity, and (2) sufcient magnesia in powderform which will be present during drying of the hydrogel to eiectsubstantial improvement in the regeneration characteristics of the beadand other desired enhanced properties.

Reference has been made above to the hot aging of the hydrogel beads inthe wet state. The purpose of this step is to control the density of thegel. Suitably aged gels have a lower bulk density indicative of a moreopen gel structure. In addition, it was found that the catalyticactivity of catalyst prepared from aged hydrogel can be more uniformlycontrolled.

The wet hydrogel beads maybe aged by maintaining them in a body ofaqueous liquid for a comparatively long time at moderate temperatures,but it is preferred to employ hot liquids at a temperature of to 160 F.in order-to accelerate the aging.- At these temperatures about 4 to 8hours aging is generally suiiicient. The aqueous liquor in which the wetbeads are conveyed may be employed as the aging medium by heating theliquid containing the hydrogel beads as a batch; or the aqueous liquormay be recirculated through a suitable heating means.

Referring again to the illustrated ilow diagram in Figure 6, thehydrogel beads after aging are washed and treated to free the same ofalkali metal. Such purification is preferably carried out to asuiiicient extent to reduce the alkali metal content of theultimate-catalyst to less than about 0.3% NazO. This may be j and whichis not deterimental thereto may be employed. Thus, the catalyst may betreated with aluminum salt solution such as aluminum sulfate and aportion of the desired alumina contentV of a silica-alumina-magnesiacatalyst thereby furnished. On the other hand, a portion of the magnesiacontent of the ultimate catalyst in addition to that provided by thecontained powder particles may be introduced by baseexchanging thehydrogel with a soluble magnesium salt such as magnesium sulfate.

The hydrogel particles after purification as above described and to arequired extent, are washed in water to remove adhering soluble saltsand then subjected to drying.

The liquid treating steps shown in the iiow sheet (Figure 6) may beoperated continuously as a counter-current system, by the provision of arequired number of treating tanks. Thus, for instance, a plurality oftanks would be provided for water washing and also five or more tanksfor base-exchanging the hydrogel beads, the treating liquid dischargedfrom one tank being successively brought to the next preceding tank. Inthis manner the final water washes and the final base exchangetreatments are carried out with the purest solutions. The dischargedliquid from the tank in which the hydrogel is first water washed will becirculated to the last base-exchanging step in the series, for fullutilization of valuable treating solution. The discharged liquid fromthe rst tank in which base-exchange is performed may be added, ifdesired, to the aging liquor.

To avoid breakage or weakening of the gel structure incident to rapidshrinkage during drying, the drying operation ordinarily must becarefully carried out. Hydrogel globules containing incorporated powderparticles of proper size and in adequate amount can be subjected to moresever and more rapid drying conditions with considerably less breakagethan hydrogels free of such powder, as disclosed in my aforesaidcopending application Serial No. 529,594.

Careful drying of `the hydrogel globules may be accomplished byprolonging the period of drying so that the rate of evaporation of waterfrom the surface does not exceed the rate of difussion of the liquidfrom the interior to the surface. Such control of evaporation rate maybe performed, for instance, by regulating the contributing factors suchas the velocity of the gaseous medium contacting the hydrogel, and thetemperature and humidity maintained during the drying period. Enicentdrying can be successfully accomplished in known manner by currents ofsuperheated steam or by the use of organic liquids forming azeotropicmixtures with water. The hydrogel beads containing incorporated powdermay be subjected to drying without previous purification or washing, and`these lliquid treating steps postponed until after drying has beeneffected.

The dried gel beads may be .calcined or 'heat treated in air, steam,inert gas, or mixtures of these, prior to use as catalysts in thehydrocarbon conversion operation. Such heat treatment need not always bepracticed, since the catalyst, as is known, will be subjected to hightemperature conditions incident to its use during hydrocarbon conversionand regeneration.

Although I do not wish to be bound by any particular theory, it isbelieved that part of the magnesia powder incorporated in the hydrosoland present in the wet hydrogel, enters into a complex chemicalcombination with the components of the sol 0r hydrogel, such as with'the silica or with the silica-alumina. In doing so, it is believed thatas to that part which,V is chemically combined, the particulate form ofthe magnesia is not retained. The small particles of magnesia stillpresent in the dried gel beads are ina-de up of the portion which hasnot been chemically combined in the complex, or which is coordinated inthe complex only at the surface of said particles. To obtain the fulladvantages of the present invention, therefore, with the retention of atleast a portion of the magnesia in particulate form during the dryingoperation, the conditions of preparation of the gel beads should be soregulated relative to the amounts of magnesia initially introduced intothe sol, that not all of the powder will enter into chemical combinationin the hydrogel. My observations lead to the belief that lowered pHbelow about pH l0 favors chemical combination of the magnesia with thesilica or silica-alumina components of the hydrogel, and accordingly thepH of the solutions employed in the purication of the wet hydrogel mustalso be controlled as well as the duration of the wet treatments,particularly in instances where only relatively small amounts ofmagnesia, say less than about 15 to 20% by weight, are initiallyintroduced in the hydrosol. On the other hand, when larger quantities ofmagnesium oxide are initially introduced, as in the order of about30%-50% by weight or more of the dry weight of the gel, a sucientquantity of powder will usually be retained as such in the beads and bepresent during drying, notwithstanding substantial time of aging of thehydrogel in the order of up to 8 hours or more. It will be understoodfrom the foregoing that in the puriication treatment of the hydrogel,the use of solutions which highly favor chemical combination of themagnesia in the siliceous hydrogel is more particularly advocated forthe treatment of hydrogels having a comparatively high magnesia powdercontent, wherein the presence of a desired residual quantity of thepowder as such during the drying of the gel is assured. Chemicalcombination of the magnesia is believed to take place more readily withincreased concentration Of magnesium ions in the treating solution,suoli as when aqueous solutions of magnesium sulfate are employed assuch for exchanging sodium, or the increased concentration of magnesiumions in solution may be due to the initial dissolution of considerableportions of the powdered magnesa from the hydrogel as might be the casewith highly acidic treating solutions.

Active silica-magnesia catalysts are obtained when such catalystscontain about 5 to 30% MgO (on total weight of catalyst composite) inchemical combination with silica. Since, however, it is preferred that aportion of the powder be retained in the gel as such (that is in a formnot `chemically combined with the silica), the amount of'powderedmagnesia incorporated will be more than that required for such chemicalcombination. By using an amount of magnesia powder equal to 30% to 50%by weight of the gel (on a dry basis), the presence of an adequateamount of powder during drying of the hydrogel is also generally takencare of.

The preferred silica-alumina-magnesia catalysts are those containing(based on dry weight ing conditions employed, may be made up of inertand insoluble powders of the type described in my copending applicationSerial No. 529,594, now U. S. Pat. No. 2,487,065.

In any of the methods heretofore described for the preparation of beads,globules of hydrosol are formed in the water immiscible liquid as aresult of the interface which exists between the hydrosol and thatliquid. The globules so formed, therefore, will be generally spheroidalor substantially spherical, having bounding surfaces corresponding tothe outline of the interface. The dried gel beads ultimately obtained bydrying of the hydrogel globules will be reduced in size as a result ofshrinkage in drying, but will conform generally to the shape of theparent globules, and

depending upon the various forces acting upon the unset globules in theformative stage, may depart from true spheres and take on more or lessthe shape of oblate spheroids, prolate spheroids, or the like. Animportant factor governing the shape of the formed bead is the rate atwhich the globules of hydrosol travel through the water immiscibleliquid, which in turn is dependent upon the relative density andviscosity of the medium employed. For instance, in a medium of lowviscosity having a density considerably less than that of the hydrosol,the globules will travel through the immiscible medium more rapidly andwill tend to assume a flatter or more disk-like shape. With a waterimmiscible medium having a density approximate to that of the hydrosol,a

slower movement of the globules of hydrosol will result, with consequentformation of more spherical beads. In the preferred operation, to obtainbeads of good sphericity, one may employ an immiscible liquid having aspecic gravity in the order of about 0.2 less than the specific gravityof the wet hydrogel, and the aqueous solution therebelow may have aspecific gravity in the order of about 0.1 less than the specificgravity of the hydrogel, so that the formed hydrogel beads will passslowly through the oil phase and through the aqueous liquid therebelow.

The following examples illustrate typical operations for the formationof catalysts in practice of the invention and should not be construed aslimitations thereon.

Example I 7.16 parts by weight of dry ground magnesium oxide powder(ignited at 1600 F. weight basis, all

- through 325 mesh) was stirred in water at room tion (NBrand)furnishing 10.5 parts by weight SiOz, and the mixture then left to standfor about 2 hours.

The silicate containing slurry was then further admixed with sulfuricacid solution of 1.050 specic gravity (containing about 3.28 parts byweight of -96% H2504) in the ratio of 60 parts by volume silicate slurryto 40 parts by volume acid, by continuously bringing together streams ofthe two liquids in a jet mixer of the type illustrated in Figures 1 and2 of the accompanying drawings. There was thereby formed a siliceoushydrosol containing hydrated magnesia which set to a firm hydrogel inabout 2.5 seconds at 25 C. having a pH of 10.

The hydrosol was ejected through a nozzle (4.7 mm. diameter) onto thesurface of a water-immiscible liquid composed of a mixture of lightmineral oil and perchlorethylene, which mixture had a specific gravityof 1.03. The mixture head and attached nozzle were rotated at 172 R. P.M.

Substantially similarly sized droplets of hydrosol were thereby formedand distributed in the immiscible liquid, which droplets set to rm gelas spheroidal globules. The gel globules passed from the immiscibleliquid into an aqueous solution of sodium sulfate (1.10 sp. gr.)therebelow, and were then transferred to an aging vat in which theglobules were aged in aqueous sodium sulfate solution (1.04 sp. gr.) forabout six hours at F.

(a) A portion of the aged gel globules was thoroughly Washed in water,and thereafter treated to remove alkali metal by washing over a periodof eight hours with dilute aqueous magnesium sulfate solution (5% byweight MgSO4 on total solution basis), the magnesium sulfate solutionbeing changed four times during the treatment; followed by extensivewater washing until the wash water was substantially sulfate free.

The washed gel was dried in a steam oven at 250 F. for eight hours.Beads of acceptable hardness were obtained with a fairly low percent ofbreakage during drying. In calcined state these beads had an apparentbulk density of 0.82 kg./liter.

(b) A second portion of the aged gel was treated similarly to (a) aboveexcept that ammonium sulfate solution was employed to remove alkalimetal. The obtained beads had an apparent bulk density of 0.62kg./liter.

The initial long standing of the magnesium oxide in the water slurryabove described effected hydration of the magnesia. It is believed thatsuch a step of aging the magnesia in water at room or elevatedtemperature for about 4 to about 24 or more hours is desirable todiminish swelling of the magnesia when in the hydrogel, which might takeplace if dry powder were directly incorporated in the hydrosol.

Example Il Silica-magnesia beads produced in accordance with theprocedure above described (Example I) were employed in cracking of alight East Texas gas oil (boiling over the range of 440 to 760 F.) at800 F., under atmospheric pressure and at a liquid space rate of 1.5(volumes of cat/volumes oil/hour) over ten-minute on-stream periods. Theyields over a number of runs were fairly consistent and averaged 40.3%gasoline by volume of charge, with the production of 3.0% coke by weightof charge, and 3.0% by Weight dry gas of 1.45 gravity.

Sillca-alumina-magnesia catalyst may be prepared in the same manner asthe silica-inagnesia catalyst illustrated in Example I, by forming asilica-alumina hydrosol instead of a silica hydrosol in which themagnesia powder is incorporated. The proportions of silica, alumina, andmagnesia may be varied over a wide range to provide catalysts of desiredproperties.

Example III To prepare a silica-alumina-magnesia catalyst containing 2%A1203 (by weight of dried catalyst) the method illustrated in Example Imay be followed, employing the reactants in the following proportions:38 parts by Weight MgO, sodium silicate to furnish S102 equivalent of 60parts by weight, sodium aluminate to furnish A1203 equivalent to 2 partsby weight, sulfuric acid solution to provide 17.8 parts by weightHzSOil.

The sodium aluminate in solution and the sodium silicate solution areadded to a slurry of the MgO (which has preferably been aged to permithydration to take place) and immediately admixed with the addition ofthe sulfuric acid. Subsequent processing may be similar to thatdescribed in Example I.

Obviously many modifications and variations of the invention ashereinbefore set forth may be made without departing from the spirit andscope thereof and therefore only such limitations should be imposed asare indicated in the appended claims.

I claim as my invention:

l. The method of preparing siliceous gel beads of improved porositycontaining magnesia in catalytically active form, which comprisesdistributing in a fast-setting siliceous hydrosol magnesia in the formof particles of a size less than 50 microns and in an amountcorresponding to 20 to 50% by weight of dried gel to -be produced,whereby a portion of the magnesia is retained in particulate form in theset gel at least during subsequent treatment including drying;suspending the hydrosol as droplets in a water-immiscible medium andsetting the droplets to form hydrogel globules containing at least partof the magnesia distributed therein in particle form, base eX- changingand washing the globules to free the same of alkali metal ions under pHconditions and during a period insufficient to eect dissolution of allof the magnesia particles in the hydrogehand drying the hydrogelglobules while containing particles of undissolved magnesia therein toform hydrogel beads.

2. The method defined in claim 1 wherein said siliceous hydrosolconsists essentially of hydrous silica and hydrous alumina.

3. The method defined in claim 1 wherein said siliceous hydrosol isprepared by interaction of an alkali-metal silicate and a solublealuminum 18 compound at a pH of 5 to 9 and a product concentration ofsilica and alumina in the reaction mixture above grams per liter.

4. The method according to claim l wherein said magnesia particles arehydrated before distribution in said siliceous hydrosol.

5. The method of preparing siliceous gel beads having an open porestructure and containing magnesia associated in the gel in catalyticallyactive form, which comprises: soaking magnesia powder in water for timesufcient to effect hydration thereof, said magnesia being of a particlesize less than 50 microns, admixing said hydrated magnesia, in quantitysuiiicient to provide 30-50 by weight of dried gel produced, withaqueous alkali metal silicate solution and with an aqueous solution of asoluble aluminum compound at a pH and in a product concentration to forma.' hydrosol capable of setting to a rm hydrogel in not more than fiveseconds; ejecting the hydrosol onto the surface of a water-immiscibleliquid of lower specific gravity than said hydrosol to form droplets ofhydrosol in said liquid, which droplets contain magnesia in particleform; setting said droplets of hydrosol to hydrogel globules whiledescending in said liquid; hot aging said globules containing magnesiain particle form therein, treating the aged globules with magnesiumsulfate solution thereby effecting release of baseexchangeably heldalkali-metal ions therefrom and causing a portion but not all of themagnesia particles to become chemically combined in the hydrogel, sothat said hydrogel contains at least about 5% magnesia therein inchemical combination; washing the hydrogel to remove soluble materials;and subjecting the washed hydrogel to drying while still containingmagnesia therein in particle form to produce dry gel beads.

'THOMAS H. MIDLIKEN, J R.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,271,319 Thomas Jan. 27, 19422,343,295 Bailie et al. Mar. 7, 1944 2,371,079 Thomas et al Mar. 6, 19452,384,945 Marisic Sept. 18, 1945 2,396,758 Stratford Mar. 19, 19462,412,958 Bates et al Dec. 24, 1946 2,435,158 Read Jan. 27, 19482,453,585 Payne et al Nov. 9, 1948 2,467,407 Ruthruff Apr. 19, 19492,470,410 Nelson May 17, 1949 2,472,831 Hunter et a1 June 14, 19492,480,627 Bodkin et al Aug. 30, 1949 2,533,278 Milliken et al Dec. 12,1950 2,551,014 Kimberlin et al. May 1, 1951 2,562,888 Bond Aug. 7, 1951

1. THE METHOD OF PREPARING SILICEOUS GEL BEADS OF IMPROVED POROSITYCONTAINING MAGNESIA IN CATALYTICALLY ACTIVE FORM, WHICH COMPRISESDISTRIBUTING IN A FAST-SETTING SILICEOUS HYDROSOL MAGNESIA IN THE FORMOF PARTICLES OF A SIZE LESS THAN 50 MICRONS AND IN AN AMOUNTCORRESPONDING TO 20 TO 50% BY WEIGHT OF DRIED GEL TO BE PRODUCED,WHEREBY A PORTION OF THE MAGNESIA IS RETAINED IN PARTICULATE FORM IN THESET GEL AT LEAST DURING SUBSEQUENT TREATMENT INCLUDING DRYING;SUSPENDING THE HYDROSOL AS DROPLETS IN A WATER-IMMISCIBLE MEDIUM ANDSETTING THE DROPLETS TO FORM HYDROGEL GLOBULES CONTAINING AT LEAST PARTOF THE MAGNESIA DISTRIBUTED THEREIN IN PARTICLE FORM, BASE EXCHANGINGAND WASHING THE GLOBULES TO FREE THE SAID OF ALKALI METAL IONS UNDER PHCONDITIONS AND DURING A PERIOD INSUFFICIENT TO EFFECT DISSOLUTION OF ALLOF THE MAGNESIA PARTICLES IN THE HYDROGEL, AND DRYING THE HYDROGELGLOBULES WHILE CONTAINING PARTICLES OF UNDISSOLVED MAGNESIA THEREIN TOFORM HYDROGEL BEADS.